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/* * Copyright (c) 1997-2018 Oracle and/or its affiliates. All rights reserved. * Copyright 2004 The Apache Software Foundation * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package javax.servlet; /** * Defines an exception that a servlet or filter throws to indicate * that it is permanently or temporarily unavailable. * * <p>When a servlet or filter is permanently unavailable, something is wrong * with it, and it cannot handle * requests until some action is taken. For example, a servlet * might be configured incorrectly, or a filter's state may be corrupted. * The component should log both the error and the corrective action * that is needed. * * <p>A servlet or filter is temporarily unavailable if it cannot handle * requests momentarily due to some system-wide problem. For example, * a third-tier server might not be accessible, or there may be * insufficient memory or disk storage to handle requests. A system * administrator may need to take corrective action. * * <p>Servlet containers can safely treat both types of unavailable * exceptions in the same way. However, treating temporary unavailability * effectively makes the servlet container more robust. Specifically, * the servlet container might block requests to the servlet or filter for a period * of time suggested by the exception, rather than rejecting them until * the servlet container restarts. * * * @author Various * */ public class UnavailableException extends ServletException { private Servlet servlet; // what's unavailable private boolean permanent; // needs admin action? private int seconds; // unavailability estimate /** * * @deprecated As of Java Servlet API 2.2, use {@link * #UnavailableException(String)} instead. * * @param servlet the <code>Servlet</code> instance that is * unavailable * * @param msg a <code>String</code> specifying the * descriptive message * */ @Deprecated public UnavailableException(Servlet servlet, String msg) { super(msg); this.servlet = servlet; permanent = true; } /** * @deprecated As of Java Servlet API 2.2, use {@link * #UnavailableException(String, int)} instead. * * @param seconds an integer specifying the number of seconds * the servlet expects to be unavailable; if * zero or negative, indicates that the servlet * can't make an estimate * * @param servlet the <code>Servlet</code> that is unavailable * * @param msg a <code>String</code> specifying the descriptive * message, which can be written to a log file or * displayed for the user. * */ @Deprecated public UnavailableException(int seconds, Servlet servlet, String msg) { super(msg); this.servlet = servlet; if (seconds <= 0) this.seconds = -1; else this.seconds = seconds; permanent = false; } /** * * Constructs a new exception with a descriptive * message indicating that the servlet is permanently * unavailable. * * @param msg a <code>String</code> specifying the * descriptive message * */ public UnavailableException(String msg) { super(msg); permanent = true; } /** * Constructs a new exception with a descriptive message * indicating that the servlet is temporarily unavailable * and giving an estimate of how long it will be unavailable. * * <p>In some cases, the servlet cannot make an estimate. For * example, the servlet might know that a server it needs is * not running, but not be able to report how long it will take * to be restored to functionality. This can be indicated with * a negative or zero value for the <code>seconds</code> argument. * * @param msg a <code>String</code> specifying the * descriptive message, which can be written * to a log file or displayed for the user. * * @param seconds an integer specifying the number of seconds * the servlet expects to be unavailable; if * zero or negative, indicates that the servlet * can't make an estimate * */ public UnavailableException(String msg, int seconds) { super(msg); if (seconds <= 0) this.seconds = -1; else this.seconds = seconds; permanent = false; } /** * * Returns a <code>boolean</code> indicating * whether the servlet is permanently unavailable. * If so, something is wrong with the servlet, and the * system administrator must take some corrective action. * * @return <code>true</code> if the servlet is * permanently unavailable; <code>false</code> * if the servlet is available or temporarily * unavailable * */ public boolean isPermanent() { return permanent; } /** * @deprecated As of Java Servlet API 2.2, with no replacement. * * Returns the servlet that is reporting its unavailability. * * @return the <code>Servlet</code> object that is * throwing the <code>UnavailableException</code> * */ @Deprecated public Servlet getServlet() { return servlet; } /** * Returns the number of seconds the servlet expects to * be temporarily unavailable. * * <p>If this method returns a negative number, the servlet * is permanently unavailable or cannot provide an estimate of * how long it will be unavailable. No effort is * made to correct for the time elapsed since the exception was * first reported. * * @return an integer specifying the number of seconds * the servlet will be temporarily unavailable, * or a negative number if the servlet is permanently * unavailable or cannot make an estimate * */ public int getUnavailableSeconds() { return permanent ? -1 : seconds; } }